It is well known that currently in an automobile using a normal engine as a power source, safety protection devices each in a fuse-form are necessarily installed in series, for safety in case of emergencies, in circuits for signal lines deployed in an automobiles to transmit signals such as radio operation commands, wiper operation commands, window opening and closing commands, turn signal commands, light switching commands and the like.
In the same way, similar safety protection devices should be installed from the standpoint of safety in an automobile using both a motor and an engine as power sources. Further, a wiring system for transmitting large power for driving the motor, which is to be the driving source, is also installed in the automobile using both the motor and the engine as the power sources. In such a wiring system which transmits such a large power, leakage currents are generated from time to time, which sometimes get into other wiring systems in their proximities.